Multi-Linear X-Ray Scanning Systems and Methods for X-Ray Scanning

ABSTRACT

A scanning transmission x-ray imaging system includes an x-ray source producing x-rays at a focal spot and moving about a source movement axis passing through the focal spot, x-ray detector arrays each detecting x-rays from the x-ray source along a detector dimension, and a collimator between the source and the arrays, fixed to the source, and defining slits to collimate the x-rays into a set of linear x-ray beams. The arrays are spaced from the source such that the linear x-ray beam at each of the arrays has the linear x-ray beam substantially impact within a height and width of a respective one of the arrays. The arrays move correspondingly with the source such that each of the linear x-ray beams remain aligned with a respective one of the arrays.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is:

-   -   a continuation of U.S. patent application Ser. No. 14/751,308,        filed on Jun. 26, 2015, which is:        -   a continuation of U.S. patent application Ser. No.            13/679,695, filed on Nov. 16, 2012, now U.S. Pat. No.            9,121,809, issued on Sep. 1, 2015 (which application claims            priority to U.S. Provisional Application Ser. No. 61/561,613            filed on Nov. 18, 2011, 61/596,487, filed on Feb. 8, 2012,            and 61/718,491, filed on Oct. 25, 2012),            the entire disclosures of which are hereby incorporated            herein by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

FIELD OF THE INVENTION

This invention relates to x-ray imaging systems and methods for x-rayscanning and, particularly, to x-ray imaging systems and methods thatuse a scanning x-ray detector.

BACKGROUND OF THE INVENTION

Transmission x-ray scanners used for personnel screening already existin the market and are used in high-security areas where access isrestricted from the general public, such as prisons, diamond and goldmines, and other places where small, high-value or dangerous items canbe smuggled into or out from a secure area. One such system is describedin U.S. Pat. No. 7,397,892 B2 to Linev, which issued on Jul. 8, 2008,and is incorporated herein in its entirety. Linev teaches the use of anx-ray source that produces a single, fan-shaped x-ray beam that iscollimated to produce a vertical beam of x-rays that is furthercollimated down to a very narrow slit. These collimated x-raysilluminate a single linear array of photo diodes coated with ascintillating phosphor. The person to be scanned stands on amotor-driven platform that moves the person slowly in between the sourceand the diode detector array exposing their entire body to the x-raybeam, thereby producing an x-ray image of their entire body. The x-rayimage then reveals any objects they may have ingested, hidden in theirclothing, or inserted in a body cavity.

The system taught by Linev, while effective because it can reveal thehidden items described above, suffers from a number of limitations. Oneof the primary limitations that the preferred embodiment of the Linevsystem suffers from is the inability to scan someone who has difficultystanding or is in a wheelchair. The platform (described in Linev as awalk-gate floor or movable door that is moving at constant speed) thatis used to move the person being screened across the x-ray beam is smalland difficult to access. It would, then, be a simple matter for a personto circumvent the scanner by claiming to need crutches, a walker, or awheelchair. The scanning speed of the platform is necessarily slow toprevent the person standing on the platform from falling down or beinginjured. The slow scanning speed reduces throughput of the system and,thereby, the rate at which people can be scanned. Another limitation ofthis system is that x-ray radiation scattered from the person beingscanned exposes anyone in the vicinity of the system to harmfulradiation. This is because the system taught by Linev does not fullyenclose and shield the walk-gate area. To mitigate this problem, a largeexclusion area around the system must be established. This exclusionarea greatly increases the amount of space required and increases thecost to install and operate the system. Any rooms adjacent to or in thefloors above or below the system would also be similarly affected bythis scattered radiation.

Yet another disadvantage of the system taught by Linev is a lack ofcontrol of the amount of radiation dose to which the person beingscanned is exposed. The Linev system teaches the use of a fixedcollimator and a detector positioning system. The exposure dose to theperson being scanned is greatly affected by the accuracy in which thex-ray beam covers the detector array. If the width of the collimated fanbeam of the x-ray source is larger than the width of the detector array,then x-rays that do not contribute to the image being formed areexposing the person being scanned, causing excess and unwarranted x-rayexposure. Linev also does not teach the use of varying the x-ray beamtechnique to optimize exposure parameters for each person being scanned.An x-ray beam technique refers to the x-ray energy (kVp), the integratedintensity (mAs), and the filtration used to acquire the image. If thesex-ray exposure parameters are not adjusted to the specific body mass andanatomical region being scanned, then the exposure used to acquire theimage is not optimal and, consequently, the dose used to acquire theimage is not minimized. This could result in over-exposure or require arepeat exposure if the parameters are inadequate for an acceptable image(underexposure).

Yet another disadvantage of the system taught by Linev is the inabilityto create different configurations of the system that could provideflexibility in the installation and use of the system in differentfacilities. There are places, for example, such as office buildings,hotels, and private residences where the need for security exists butthe physical presence of x-ray systems and equipment creates problemswith available space and a desire to obscure or hide the securityapparatus from view.

SUMMARY OF THE INVENTION

The multi-linear x-ray scanner and methods for scanning described hereinovercome certain limitations of existing transmission x-ray scanners byusing a novel design that permits different configurations toaccommodate the user's individual needs. The multi-linear x-ray scannercontains no external moving parts that require secure mounting or thatrestrict the movement of people coming in and out of the scanner. As aresult, the multi-linear x-ray scanner offers distinct advantages interms of work flow, security options, and aesthetics.

The multi-linear x-ray scanner can be constructed out of two or threeseparate cabinet features: a generator cabinet; an imaging cabinet; andan optional scanning cabinet or booth. The scanning booth can completelysurround (and, if necessary, by adding a ceiling feature, even enclose)the generator and imaging cabinets, or the system can have an openconfiguration without any enclosure. In other words, the scanning boothcan operate as a “closed” system (which, for example, uses a wall, doorand/or curtain type of shielding to completely surround the scanningsubject) or a “partially-closed” system (which, alternatively forexample, uses walls, partitions, or curtains to partially enclose thescanning subject). Both of these configurations thus provide physicalshielding for the scattered x-ray radiation emitting from the personduring the scan (more commonly known as radiation scatter) to protectothers in the immediate vicinity from radiation scatter.

In an entirely open system configuration, the generator and imagingcabinets are not surrounded by any shielding; rather, an exclusion orbuffer zone surrounding the system can be used to protect others in theimmediate vicinity from radiation scatter.

In another alternative embodiment, the generator cabinet and imagingcabinet can be placed within or behind walls of a room or hallway tohide them from view. To place such a cabinet/cabinets behind awall/walls, the walls would need x-ray translucent panels to allow thex-rays to penetrate through the walls and/or floor.

With the foregoing and other objects in view, there is provided, ascanning transmission x-ray imaging system including an x-ray sourceproducing x-rays at a focal spot and moving about a source movement axispassing through the focal spot, at least two x-ray detector arrays eachhaving a detector dimension and detecting x-rays from the x-ray sourcealong the detector dimension, a collimator disposed between the x-raysource and the at least two detector arrays, fixed to the x-ray source,and defining at least two slits to collimate the x-rays into a set oflinear x-ray beams, the at least two x-ray detector arrays being spacedfrom the x-ray source such that the linear x-ray beam at each of the atleast two x-ray detector arrays has the linear x-ray beam substantiallyimpact within the height and width of a respective one of the at leasttwo x-ray detector arrays, and the at least two x-ray detector arraysmoving correspondingly with the x-ray source such that each of thelinear x-ray beams remain aligned with a respective one of the at leasttwo x-ray detector arrays.

With the objects in view, there is also provided a scanning transmissionx-ray imaging system including a stationary x-ray source producingx-rays at a focal spot and defining a source focal spot axis passingthrough the focal spot, at least two x-ray detector arrays having adetector dimension and detecting the x-rays from the x-ray source alongthe detector dimension, a collimator moving about the source focal spotaxis, being disposed between the x-ray source and the at least twodetector arrays, and defining at least two slits to collimate the x-raysinto a set of linear x-ray beams each having a height and a width, andthe at least two x-ray detector arrays being spaced from the x-raysource such that each of the linear x-ray beams substantially impactwithin the height and width of a respective one of the at least twox-ray detector arrays, the at least two x-ray detector arrays movingcorrespondingly with the collimator such that each of the linear x-raybeams remains aligned with the respective one of the at least two x-raydetector arrays.

With the objects in view, there is also provided a scanning transmissionx-ray imaging system including an x-ray source producing x-rays at afocal spot and moving about a source movement axis passing through thefocal spot, at least two x-ray detector arrays each having a detectordimension and detecting x-rays from the x-ray source along the detectordimension, a horizontal platform under which is disposed one of the atleast two x-ray detector arrays, the platform being substantially x-raytransparent, a collimator disposed between the x-ray source and the atleast two detector arrays, fixed to the x-ray source, and defining atleast two slits to collimate the x-rays into a set of linear x-raybeams, the at least two x-ray detector arrays being spaced from thex-ray source such that the linear x-ray beam at each of the at least twox-ray detector arrays has the linear x-ray beam substantially impactwithin the height and width of a respective one of the at least twox-ray detector arrays, and the at least two x-ray detector arrays movingcorrespondingly with the x-ray source such that each of the linear x-raybeams remain aligned with a respective one of the at least two x-raydetector arrays.

With the objects in view, there is also provided a scanning transmissionx-ray imaging system including an x-ray source producing x-rays at afocal spot and moving about a source movement axis passing through thefocal spot, at least one x-ray detector array having a detectordimension and detecting x-rays from the x-ray source along the detectordimension, a collimator disposed between the x-ray source and the atleast one detector array, fixed to the x-ray source, and defining atleast one slit to collimate the x-rays into a linear x-ray beam;, the atleast one x-ray detector array being spaced from the x-ray source suchthat the linear x-ray beam at the at least one x-ray detector array hasthe linear x-ray beam substantially impact within the height and widthof the at least one x-ray detector array, and the at least one x-raydetector array moving correspondingly with the x-ray source such thatthe linear x-ray beam remains aligned with the at least one x-raydetector array.

With the objects in view, there is also provided a scanning transmissionx-ray imaging system including an x-ray source producing x-rays at afocal spot and moving about a source movement axis passing through thefocal spot, at least two x-ray detector arrays each having a detectordimension and detecting x-rays from the x-ray source along the detectordimension, a horizontal platform under which is disposed one of the atleast two x-ray detector arrays, the platform being substantially x-raytransparent, a collimator disposed between the x-ray source and the atleast two detector arrays, fixed to the x-ray source, and defining atleast one slit to collimate the x-rays into a linear x-ray beam, the atleast two x-ray detector arrays being spaced from the x-ray source suchthat the linear x-ray beam substantially impacts within the height andwidth of both of the at least two x-ray detector arrays, and the atleast two x-ray detector arrays moving correspondingly with the x-raysource such that the linear x-ray beam remains aligned with the at leasttwo x-ray detector arrays.

In accordance with another feature, there is provided an x-rayprocessing unit processing detection of the linear x-ray beams by the atleast two x-ray detector arrays.

In accordance with a further feature, there is provided at least onemotor controlled by the x-ray processing unit and moving the x-raysource about the source movement axis to pivot the linear x-ray beamsabout the focal spot and create an x-ray emission pyramid and moving theat least two x-ray detector arrays correspondingly with the x-ray sourcesuch that each of the linear x-ray beams remains aligned with arespective one of the at least two x-ray detector arrays.

In accordance with an added feature, the x-ray processing unit forms atwo-dimensional transmission x-ray image of an object disposed betweenthe collimator and the at least two x-ray detector arrays within thex-ray emission pyramid when the linear x-ray beams are panned across theobject.

In accordance with an additional feature, the at least two x-raydetector arrays are two horizontally disposed x-ray detector arrays, onemoving horizontally and one moving vertically.

In accordance with yet another feature, the at least two x-ray detectorarrays are two horizontally disposed x-ray detector arrays, onevertically disposed and moving horizontally and one horizontallydisposed and moving horizontally.

In accordance with yet a further feature, the x-ray processing unitmoves the x-ray source with a variable speed to optimize x-ray exposurefor different portions of the object being scanned.

In accordance with yet an added feature, at least one motor controlledby the x-ray processing unit and moving the collimator about the sourcefocal spot axis to, thereby, move the linear x-ray beam and create anx-ray emission pyramid and moving the at least two x-ray detector arrayscorrespondingly with the collimator such that the linear x-ray beamsremain aligned with the respective one of the at least two x-raydetector arrays.

In accordance with a concomitant feature, the at least two x-raydetector arrays are two x-ray detector arrays, one vertically disposedand moving horizontally and one horizontally disposed and movinghorizontally.

Although the invention is illustrated and described herein as embodiedin a multi-linear x-ray scanner and methods for scanning, it is,nevertheless, not intended to be limited to the details shown becausevarious modifications and structural changes may be made therein withoutdeparting from the spirit of the invention and within the scope andrange of equivalents of the claims. Additionally, well-known elements ofexemplary embodiments of the invention will not be described in detailor will be omitted so as not to obscure the relevant details of theinvention.

Additional advantages and other features characteristic of the presentinvention will be set forth in the detailed description that follows andmay be apparent from the detailed description or may be learned bypractice of exemplary embodiments of the invention. Still otheradvantages of the invention may be realized by any of theinstrumentalities, methods, or combinations particularly pointed out inthe claims.

Other features that are considered as characteristic for the inventionare set forth in the appended claims. As required, detailed embodimentsof the present invention are disclosed herein; however, it is to beunderstood that the disclosed embodiments are merely exemplary of theinvention, which can be embodied in various forms. Therefore, specificstructural and functional details disclosed herein are not to beinterpreted as limiting, but merely as a basis for the claims and as arepresentative basis for teaching one of ordinary skill in the art tovariously employ the present invention in virtually any appropriatelydetailed structure. Further, the terms and phrases used herein are notintended to be limiting; but rather, to provide an understandabledescription of the invention. While the specification concludes withclaims defining the features of the invention that are regarded asnovel, it is believed that the invention will be better understood froma consideration of the following description in conjunction with thedrawing figures, in which like reference numerals are carried forward.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, which are not true to scale, and which, together with thedetailed description below, are incorporated in and form part of thespecification, serve to illustrate further various embodiments and toexplain various principles and advantages all in accordance with thepresent invention. Advantages of embodiments of the present inventionwill be apparent from the following detailed description of theexemplary embodiments thereof, which description should be considered inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of an exemplary embodiment of animplementation of an x-ray beam forming and imaging system including ashielded housing containing an x-ray generator, a filter, a dosimeter,and a collimator with a plurality of horizontal x-ray beams passingthrough a person being scanned and impinging on a detector arrayincluding a plurality of linear x-ray detectors;

FIG. 2 is a block and schematic circuit diagram of an exemplaryembodiment of an implementation of an image acquisition system withmicroprocessor controller that interact with one another to controlproduction of x-rays and formation of an image with the x-ray generatornot shown in the drawing;

FIG. 3 is an elevational view of an exemplary embodiment of an x-raydetector from a detector side;

FIG. 4 is a fragmentary, perspective view of the x-ray detector of FIG.3 with an impinging x-ray beam;

FIG. 5 is an elevational view of the x-ray detector of FIG. 3 fromopposite the detector side;

FIG. 6 is a perspective view of the x-ray detector of FIG. 3 from thedetector side;

FIG. 7 is a right-side elevational view of the x-ray detector of FIG. 3;

FIG. 8 is an elevational view of an exemplary embodiment of an x-raydetector array having a plurality of the x-ray detectors of FIG. 3 froma detector side;

FIG. 9 is an elevational view of the x-ray detector array of FIG. 8 fromopposite the detector side;

FIG. 10 is a perspective view of the x-ray detector array of FIG. 8;

FIG. 11 is a schematic side elevational view of an exemplary embodimentof a multi-linear x-ray scanner having a partially-closed configurationthat includes a scanning booth with a retractable curtain to completelycover the entry point and, thereby, complete an x-ray enclosure;

FIG. 12 is a schematic top plan view of the multi-linear x-ray scannerof FIG. 11;

FIG. 13 is a schematic top plan view of an exemplary embodiment of amulti-linear x-ray scanner having a partially-closed configuration thatincludes a scanning booth without completely covering the entry pointbut with a partition offset from a plane of the detector array so thatthe scanning subject sits or stands behind an alcove-like cavity thatcreates a shielded area to apply a technique referred to as“shadow-shielding” that reduces an exposure dose around the booth;

FIG. 14 is a schematic side elevational view of the multi-linear x-rayscanner of FIG. 13 from a door side of the scanner booth;

FIG. 15 is a schematic top plan view of an exemplary embodiment of amulti-linear x-ray scanner with a configuration that includes only agenerator cabinet and an imaging cabinet, neither of which are enclosed,to result in an open scanning area utilizing no external shieldingdesirable where a small footprint is required;

FIG. 16 is a schematic side elevational view of the multi-linear x-rayscanner of FIG. 15;

FIG. 17 is a schematic top plan view of another exemplary embodiment ofa multi-linear x-ray scanner with the generator and imaging cabinetsrecessed in or positioned behind walls where the walls and the space inbetween form the scanning area;

FIG. 18 is a schematic side elevational view of the multi-linear x-rayscanner of FIG. 17;

FIG. 19 is a side elevational view of an exemplary embodiment of amulti-linear x-ray scanner with the generator cabinet removed butshowing a collimator and with a detector array sub-assembly in a raisedposition;

FIG. 20 is a perspective view of the multi-linear x-ray scanner of FIG.19;

FIG. 21 is a side elevational view of the multi-linear x-ray scanner ofFIG. 19 with the detector array sub-assembly in an intermediateposition;

FIG. 22 is a perspective view of the multi-linear x-ray scanner of FIG.21;

FIG. 23 is a side elevational view of the multi-linear x-ray scanner ofFIG. 19 with the detector array sub-assembly in a lowered position;

FIG. 24 is a perspective view of the multi-linear x-ray scanner of FIG.23;

FIG. 25 is a fragmentary, enlarged, side elevational view of themulti-linear x-ray scanner of FIG. 23;

FIG. 26 is a side elevational view of an exemplary embodiment of amulti-linear x-ray scanner with a portion of the generator cabinetremoved and with a collimator and a detector array sub-assembly in araised position scanning a wheelchair;

FIG. 27 is a side elevational view of the multi-linear x-ray scanner ofFIG. 26 with the collimator and the detector array sub-assembly in anintermediate position;

FIG. 28 is a side elevational view of the multi-linear x-ray scanner ofFIG. 26 with the collimator and the detector array sub-assembly in alowered position;

FIG. 29 is a fragmentary, enlarged, perspective view of a portion of thegenerator cabinet of FIG. 26 from a front side thereof;

FIG. 30 is a fragmentary, enlarged, side elevational view of the portionof the generator cabinet of FIG. 29 from a right side thereof with thecollimator in a raised position;

FIG. 31 is a fragmentary, enlarged, side elevational view of the portionof the generator cabinet of FIG. 29 from a right side thereof with thecollimator in an intermediate position;

FIG. 32 is a fragmentary, enlarged, side elevational view of the portionof the generator cabinet of FIG. 29 from a right side thereof with thecollimator in a lowered position;

FIG. 33 is a fragmentary, enlarged, perspective view of the portion ofthe generator cabinet of FIG. 32 from in front the right side thereof;

FIG. 34 is a side elevational view of the multi-linear x-ray scanner ofFIG. 26 with a collimator and a detector array sub-assembly in a raisedposition scanning a person;

FIG. 35 is a side elevational view of the multi-linear x-ray scanner ofFIG. 34 with the collimator and the detector array sub-assembly in anintermediate position;

FIG. 36 is a side elevational view of the multi-linear x-ray scanner ofFIG. 34 with the collimator and the detector array sub-assembly in alowered position;

FIG. 37 is a side elevational view of the multi-linear x-ray scanner ofFIG. 26 with the collimator and the detector array sub-assembly in araised position;

FIG. 38 is a side elevational view of the multi-linear x-ray scanner ofFIG. 37 with the collimator and the detector array sub-assembly in anintermediate position;

FIG. 39 is a side elevational view of the multi-linear x-ray scanner ofFIG. 37 with the collimator and the detector array sub-assembly in alowered position;

FIG. 40 is a fragmentary, perspective view of an exemplary embodiment ofa multi-linear x-ray scanner from a front side thereof with a portion ofthe generator cabinet removed and with a collimator pivoted to anintermediate position;

FIG. 41 is a fragmentary, partially cross-sectional, perspective view ofthe multi-linear x-ray scanner of FIG. 40 from behind a side thereof;

FIG. 42 is a perspective view of the multi-linear x-ray scanner of FIG.40 with the collimator and detector arrays in a raised position;

FIG. 43 is a perspective view of the multi-linear x-ray scanner of FIG.40 with the collimator and detector arrays in an intermediate position;

FIG. 44 is a top plan view of the multi-linear x-ray scanner of FIG. 40with the collimator and detector arrays in a raised position;

FIG. 45 is a top plan view of the multi-linear x-ray scanner of FIG. 40with the collimator and detector arrays in an intermediate position;

FIG. 46 is a top plan view of the multi-linear x-ray scanner of FIG. 40with the collimator and detector arrays in a lowered position;

FIG. 47 is a perspective view of the collimator of the multi-linearx-ray scanner of FIG. 40;

FIG. 48 is a left side elevational view of the collimator of themulti-linear x-ray scanner of FIG. 40;

FIG. 49 is a front side elevational view of the collimator of themulti-linear x-ray scanner of FIG. 40;

FIG. 50 is a top plan side view of the collimator of the multi-linearx-ray scanner of FIG. 40 from a left side thereof;

FIG. 51 is a side elevational view of the multi-linear x-ray scanner ofFIG. 40 with the collimator pivoted to a raised position to scan awheelchair;

FIG. 52 is a side elevational view of the multi-linear x-ray scanner ofFIG. 51 with the collimator pivoted to an intermediate position;

FIG. 53 is a side elevational view of the multi-linear x-ray scanner ofFIG. 51 with the collimator pivoted to a lowered position;

FIG. 54 is a perspective view of the multi-linear x-ray scanner of FIG.40 with the collimator pivoted to a raised position to scan a person;

FIG. 55 is a perspective view of the multi-linear x-ray scanner of FIG.54 with the collimator pivoted to an intermediate position;

FIG. 56 is a perspective view of the multi-linear x-ray scanner of FIG.54 with the collimator pivoted to a lowered position;

FIG. 57 is a fragmentary, perspective and partially transparent view ofan exemplary embodiment of a multi-linear x-ray scanner from a frontside thereof with a portion of the generator cabinet removed and with acollimator and scanner arrays pivoted to a left position;

FIG. 58 is a fragmentary, enlarged, perspective view of the multi-linearx-ray scanner of FIG. 57 from behind a left side thereof;

FIG. 59 is a fragmentary, further enlarged, perspective view of themulti-linear x-ray scanner of FIG. 57 from behind a left side thereof;

FIG. 60 is a top plan view of the multi-linear x-ray scanner of FIG. 57;

FIG. 61 is a top plan view of the multi-linear x-ray scanner of FIG. 57with the collimator and scanner arrays pivoted to a centered position;

FIG. 62 is a top plan view of the multi-linear x-ray scanner of FIG. 57with the collimator and scanner arrays pivoted to a right position;

FIG. 63 is a bottom plan view of the multi-linear x-ray scanner of FIG.57 with the collimator and scanner arrays pivoted to an intermediateright position;

FIG. 64 is a perspective view of the multi-linear x-ray scanner of FIG.57 from a front right side thereof and scanning a wheelchair with thecollimator and scanner arrays pivoted to a left position;

FIG. 65 is a perspective view of the multi-linear x-ray scanner of FIG.64 with the collimator and scanner arrays pivoted to a centeredposition;

FIG. 66 is a perspective view of the multi-linear x-ray scanner of FIG.64 with the collimator and scanner arrays pivoted to a rightintermediate position;

FIG. 67 is a perspective view of the multi-linear x-ray scanner of FIG.57 from a front right side thereof and scanning a person with thecollimator and scanner arrays pivoted to a left intermediate position;and

FIG. 68 is a perspective view of the multi-linear x-ray scanner of FIG.64 with the collimator and scanner arrays pivoted to a centeredposition.

DETAILED DESCRIPTION OF THE EMBODIMENTS

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which can be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. Further, the terms and phrases usedherein are not intended to be limiting; but rather, to provide anunderstandable description of the invention. While the specificationconcludes with claims defining the features of the invention that areregarded as novel, it is believed that the invention will be betterunderstood from a consideration of the following description inconjunction with the drawing figures, in which like reference numeralsare carried forward.

Alternate embodiments may be devised without departing from the spiritor the scope of the invention. Additionally, well-known elements ofexemplary embodiments of the invention will not be described in detailor will be omitted so as not to obscure the relevant details of theinvention.

Before the present invention is disclosed and described, it is to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting. The terms “a” or “an”, as used herein, are defined as one ormore than one. The term “plurality,” as used herein, is defined as twoor more than two. The term “another,” as used herein, is defined as atleast a second or more. The terms “including” and/or “having,” as usedherein, are defined as comprising (i.e., open language). The term“coupled,” as used herein, is defined as connected, although notnecessarily directly, and not necessarily mechanically.

Relational terms such as first and second, top and bottom, and the likemay be used solely to distinguish one entity or action from anotherentity or action without necessarily requiring or implying any actualsuch relationship or order between such entities or actions. The terms“comprises,” “comprising,” or any other variation thereof are intendedto cover a non-exclusive inclusion, such that a process, method,article, or apparatus that comprises a list of elements does not includeonly those elements but may include other elements not expressly listedor inherent to such process, method, article, or apparatus. An elementproceeded by “comprises . . . a” does not, without more constraints,preclude the existence of additional identical elements in the process,method, article, or apparatus that comprises the element.

As used herein, the term “about” or “approximately” applies to allnumeric values, whether or not explicitly indicated. These termsgenerally refer to a range of numbers that one of skill in the art wouldconsider equivalent to the recited values (i.e., having the samefunction or result). In many instances these terms may include numbersthat are rounded to the nearest significant figure.

The terms “program,” “software,” “software application,” and the like asused herein, are defined as a sequence of instructions designed forexecution on a computer system. A “program,” “software,” “computerprogram,” or “software application” may include a subroutine, afunction, a procedure, an object method, an object implementation, anexecutable application, an applet, a servlet, a source code, an objectcode, a shared library/dynamic load library and/or other sequence ofinstructions designed for execution on a computer system.

Herein various embodiments of the present invention are described. Inmany of the different embodiments, features are similar. Therefore, toavoid redundancy, repetitive description of these similar features maynot be made in some circumstances. It shall be understood, however, thatdescription of a first-appearing feature applies to the later describedsimilar feature and each respective description, therefore, is to beincorporated therein without such repetition.

Described now are exemplary embodiments of the scanning systems andmethods. Referring now to the figures of the drawings in detail andfirst, particularly to FIGS. 1 and 2, there is shown an x-ray source 1as a monoblock generator capable of producing a fan beam of x-rays witha maximum energy of at least 150 keV and a maximum tube current of atleast 3 milliamperes. An example of such a generator is made by SpellmanHigh Voltage Electronics Corporation (model XRB201) in Hauppauge, NewYork. The x-ray generator is mounted on a platform 2 to 3 feet high andhoused in a lead-lined cabinet with the x-ray output pointed toward adetector assembly 6 having at least one detector array 8 (see FIG. 2),an example of which can be a photodiode array. Examples of the array 8are made by X-Scan Imaging Corporation and another Hamamatsu Photonics,K.K. A filter wheel 2 containing one or more filters made of aluminumand copper of varying thicknesses (Al 1-2 mm, Cu 0.1-0.2 mm) is placedin close proximity (within a few centimeters) to the output of thegenerator to intercept and filter the x-ray beam. A collimator 3containing a plurality of horizontal slits is placed adjacent the filter2 to intercept and collimate the filtered x-ray beam into a plurality ofhorizontal beams of x-rays such that the height of the x-ray beams arethe same dimension as the photodiodes in the detector arrays 8. Thecollimator 3 is moved up and down by a motor 13 that is controlled by amicroprocessor controller 16. The microprocessor controller 16 receivesdata from an encoder 12 mounted on the collimator assembly that providesdata on the position and speed of the collimator 3. X-rays emitted bythe collimator 3 pass through an aperture 4 that confines the dimensionand movement of the x-ray beams 5 within the active area defined by thedetector arrays 8, which are moved along vertical supports 7 by a slidedrive motor 11. The position and speed of the detector arrays 8 ismonitored by an encoder 10 that sends data to the microprocessorcontroller 16.

Each detector array 8 in the embodiment of a photodiode array is alinear array containing a plurality of individual photodiodes. In anexemplary embodiment, there are a total of 320 diodes in each array 8and a total of three individual linear arrays 8. The length of theindividual linear arrays 8 is approximately 28 inches. Each of theselinear arrays 8 is illuminated by the collimated x-ray beams 5 emittedby the x-ray source 1. When the amount of x-rays is absorbed in thediode array to produce an adequate exposure, the diode arrays are readout and three rows of the x-ray image are formed. The slide motor drive11 for the diode array then indexes the size of a photodiode (2.5 mm)and rests while the diodes acquire another exposure to acquire threeadditional rows of pixels in the output x-ray image. This process isrepeated until the entire length of the image size has been scanned. Theslide motor 11 moves the arrays 8 a total distance of 670 mm (26inches), thereby simultaneously creating three images that are 28 incheswide and 26 inches tall. These three images are stacked one on top ofanother and are stitched together by the image processing software orprogram in the workstation 17 to produce a composite image that is twometers tall (78 inches) by 0.67 meters wide (28 inches).

In accordance with an exemplary embodiment, the arrays 8 are photodiodearrays manufactured by Detection Technology Oy (Micropolis, Finland).The photodiodes are mounted on a linear array x-ray detector card(X-Card SE). In one exemplary embodiment, fifteen X-Cards (five cards oneach of the three separate linear arrays 8) are connected to a singledata acquisition board (X-DAQ) associated with the workstation 17 and/orthe microcontroller 16. Each X-Card contains sixty-four photodiodes. TheX-DAQ contains on-board signal processing functions and real-time imagedata acquisition to send to the computer workstation 17, for example,via Ethernet.

One exemplary embodiment of an x-ray detector card 300 usable in thevarious embodiments described herein is shown in FIGS. 3 to 7. The card300 has a detector side 310 on which resides an x-ray detector 312.Here, there are four individual x-ray detectors 312 set along an axisthat is to be aligned with an incoming beam of x-rays, as shown, forexample, by the beam 5 in FIG. 4. Various views of the card 300 areshown in FIGS. 5, 6, and 7. The card 300 is modular and, therefore, canbe set up in a linear array 8 of photodiodes shown, for example, inFIGS. 8, 9, and 10. Appropriate connectors 1000 can be used to securethe array 8 to the vertical support 7 of the detector assembly 6 formovement, for example, effected by the slide motor drive 11, or to anyother detector assembly described herein in the various exemplaryembodiments.

The technique factors (filtration, kV, mA, and exposure time) used toexpose the person being scanned are optimized by software installed onthe workstation 17. This software monitors the exposure level of thearrays 8 and data from the microprocessor controller 16 while the x-raybeams 5 are exposing the arrays 8 to adjust the technique factorsproduced by the x-ray generator 1 such that the intensity and contrastof the x-ray image is maximized while the exposure dose is minimized foreach person being scanned. This program is similar in nature to programsand devices used by medical diagnostic x-ray equipment for fluoroscopicimaging to dynamically control exposure and image quality commonlyreferred to as Automatic Brightness Systems (ABS).

In accordance with an exemplary embodiment utilizing photodiode arrays,the ABS system is carried out by taking the digital output value fromeach photodiode after exposure, defining a region of anatomical exposure(those photodiodes located behind the person and not directly exposed tothe x-ray source), and averaging those values into a single value. Thissingle average value is then compared to a target value that is equal toone half of the saturated value of the photodiode (from an exposure justlarge enough to saturate the photodiode). If the average value is lowerthan the target value, then the x-ray intensity (mA) is increased or thekV of the x-ray spectrum is increased to drive the average value to thetarget value during the next line of exposure. Conversely, if theaverage value is higher than the target value, then the kV and mA valuesare lowered. Alternatively, the scanning speed could be adjusted tochange the exposure time for each photodiode, thereby changing the mAsor integrated exposure value. The kV and mA values are changed accordingto a pre-determined relationship or look-up table (LUT) that is createdand optimized by experimentation with the image quality produced atvarious x-ray technique values (kV and mA) using anatomically correctphantoms.

In an alternative exemplary embodiment, dedicated single photodiodes 9are mounted on each of the individual arrays 8 of photodiodes 9. Thesephotodiodes 9 are exposed and produce the digital output value used tocompare with the target value. Accordingly, the shape of the collimatoropenings have notches in them to permit x-rays to pass through andexpose the photodiodes 9.

An exemplary method of operating the x-ray scanner begins when theoperator initializes the scanner from the GUI on workstation 17. Theperson to be scanned enters the scanner through an opening in thescanner housing 18 created by the sliding shielded door 19 as shown, forexample, in FIGS. 11 and 12. The person enters the scanner by walking upa ramp 20 and stands facing the x-ray generator 1 on a platform 21. Aperson using a walker, crutches, or a wheelchair can also enter thescanner on the ramp 20. The platform 21 and all interior surfaces of thescanning area are made from a material that is transparent to x-rays andis structurally sound, such as a carbon-fiber composite. Once the personis properly positioned, the sliding door 19 closes and the x-ray scan isinitiated. Approximately 0.5 seconds later, the scan is complete and, ifthe operator is satisfied with the quality of the image, the door 19 isopened.

The image produced by the scanner can be studied to determine if anyitems of interest are hidden on the person being scanned. The images canbe saved on a memory (e.g., a hard drive) of the workstation 17 forlater review. The dose used to acquire each image can also be stored aswell.

Safe operation of the scanner is ensured by the use of severalinterlocks 15 that are connected to, but are not limited to, the slidingdoor 19, the x-ray generator 1, the array 8, and other components suchas the collimator 3 to ensure that x-rays are not emitted unless thedoor is closed and that x-rays are properly aligned with the movement ofthe array 8. The interlocks 15 are managed by the microprocessorcontroller 16.

FIGS. 13 to 18 show other exemplary embodiments of a scanning systemthat can be configured in several different ways to accommodate theneeds of different market applications. For example, as shown in FIGS.13 and 14, the system can be configured to eliminate the sliding door 19and to move the door opening 22 to the scanner housing 18 away from theplane of the array 8 to create a shielded cavity 23 that can shieldscattered x-rays produced during a scan. In this exemplary,configuration there no need for a sliding door 19, thereby reducing thecost of the system and simplifying the operation of the system.

Another system configuration can be created by eliminating the scannerhousing 18 entirely. In this exemplary configuration, illustrated inFIGS. 15 and 16, all of the components that produce the scanning x-raybeams 5 including the x-ray source 1, filter wheel 2, collimator 3 andaperture 4 are enclosed in a lead-lined generator cabinet 30. All of thecomponents used to make the image including the arrays 8, verticalsupport 7, slide drive motors 11 and encoder 19, and microprocessorcontroller are enclosed in an imaging cabinet 31. The position anddistance between the generator cabinet 30 and the imaging cabinet 31must be precisely controlled and is dictated by the geometry of thescanning system. In particular, the cone beam width of the x-ray source1 and array 8 (e.g., the number of photodiodes in the array) of thescanner determine the relative position and distance between the twocabinets. The platform 21 is placed in the space between the cabinets toform an open scanning area having no shielded walls. The platform 21allows the arrays 8 to scan below the level of the feet of the personbeing scanned to create a view of their shoes and feet.

An advantage of this “open” configuration is that the system can beinstalled in buildings and rooms such that none of the components of thesystem are visible. This configuration can be created by placing thegenerator cabinet 30 behind or in a wall 32 of a room or hallway andplacing the imaging cabinet 31 behind or in an opposing wall, as shownin FIGS. 17 and 18. The opposing walls 32 of the room or hallway arecloser together than the distance required between the generator cabinet30 and the imaging cabinet 31. The walls 32 have x-ray translucentmaterials, such as a carbon-fiber composite, to minimize the x-rayattenuation and scatter. To avoid the need of a raised platform 21, theimaging cabinet 31 can be placed several inches or more below groundlevel to allow imaging of the feet and shoes. In such a configuration,none of the components of the system are visible to anyone, providingvery discrete measures for providing security in facilities like hotels,private residences, and other venues where the security apparatus mustkeep a very low profile.

Another advantage of the open cabinet design is that the scanner housing18 can be customized to provide additional security and safety features.The need for such additional features is particularly important in areasof the world where terrorists are known to operate. Specifically, it isadvantageous to make the scanner housing 18 blast-proof and/orbullet-proof. This feature protects occupants of the building from asuicide bomber setting off a bomb when confronted with discovery. Otherfeatures could be incorporated in the scanner housing 18 including bothlethal and non-lethal measures for subduing an armed and dangerousperson being scanned.

In accordance with an exemplary embodiment shown in FIGS. 19 to 25, itis advantageous to mechanically link the collimator 3 and the arrays 8with an arm 50 that pivots about a point in space parallel to the focalspot of the x-ray source 1. The collimator 3 is attached to the arm 50in a position so that it rotates on the circumference of a circle thatlies in a plane intersecting the x-ray source 1 focal spot with a centerthat is also located at the focal spot of the x-ray source 1. The arrays8 are mounted on a second arm 52 that is attached and perpendicular tothe end of arm 50 opposite the pivot point 51 so that, together, the twoarms 50, 52 are approximately L-shaped. The second support arm 52 iscurved facing the focal spot of the x-ray source 1 with a radius equalto the distance to the focal spot of the x-ray generator 1. In thismanner, the arm 50 can be rotated about its pivot point 51 to produce aset of scanning x-ray beams 5 that will remain in alignment with andperpendicular to the arrays 8 mounted on the support arm 52 at all timesduring a scan. In this way, during a scan, the arm 50 is rotated so thatthe collimator 3 and arrays 8 sweep vertically to expose a person orobject standing on the platform while the x-ray source 1 remainsstationary as shown in the progression of FIGS. 19, 21, and 23 or 20,22, and 24. Various portions of the x-ray source are eliminated forreasons of clarity

A person standing on the platform 21 with their back against the frontwall 1900 of the imaging cabinet 31 would have their feet project out infront of the wall 1900 by at least a foot and, possibly, sixteen inches.To acquire an image that would include the feet of such a person, it isnecessary to bring the scanning arm 52 down below the height of theplatform 21 so that the lowest x-ray beam 5 can expose the person'sfeet. Such an orientation is illustrated in FIGS. 23 and 24. In thisexemplary embodiment, even if the support arm 52 was brought down untilit touched the floor as shown, the platform 21 would have to be at least11 inches high in order to provide enough clearance for the support arm52 to reach far enough below the platform to scan 16 inches in front ofthe imaging cabinet 31, the geometry of which is illustrated in FIG. 25.

If a person to be scanned was sitting in a wheelchair, the platform 21would have to be raised even higher. In such a situation, forward partsof the seated person might be located twenty-four or more inches awayfrom the wall 1900. This presents a problem with the overall height andarea that the system of FIGS. 19 to 25 would occupy and is a significantlimitation of this exemplary embodiment because, according to most rulesregarding wheelchairs, a wheelchair ramp 20 must be at least twelveinches long for every inch of height. Accordingly, a ramp for aneleven-inch platform height would have to be eleven feet long. If theplatform 21 is even higher to accommodate a person in a wheelchair, theramp 20 would be significantly longer than eleven feet, which is costlyand, in many cases, architecturally problematic. Another limitation ofthis exemplary embodiment is that the mechanical arm 50 blocks accessalong one side of the platform 21. This configuration, in particular,requires people to enter and leave the platform from the same side.

In order to scan people sitting in wheelchairs 40, therefore, anotherexemplary embodiment of the system scans along the underside of theplatform 21 in addition to the front wall 1900 of the imaging cabinet31. In accordance with this exemplary embodiment shown in FIGS. 26 to40, the detector arrays 8 are mounted on a set of horizontal rails—twoof the arrays 8 being mounted behind the 1900 wall of the imagingcabinet 31 and one array 8 being mounted under the platform 21. Each ofthe three arrays 8 are driven by separate drive motors 11. The positionof each array 8 is measured by separate encoders 10. In thisconfiguration, the mechanical arms 50 and 52 are, therefore, replaced byindependently controlled motors 11 that move the arrays 8 synchronouslywith the x-ray beams 5 as the collimator 3 sweeps through its verticalmotion. Synchronizing the motion of the arrays 8 with the motion of thex-ray beams 5 can be accomplished by a feedback mechanism where theoutput of one or more of the photodiodes 9 on the extreme ends of eacharray 8, for example, are used to control the motion of each of thearrays by adjusting the speed of each drive motor 11 so that theintensity of the output from the photodiodes 9 is maintained at amaximum value during the scan. Alternatively, a set of sentinelphotodiodes 9 are mounted directly above and below each of the arrays 8to sense the x-ray beams 5. If any of the arrays 8 moves out ofalignment with their respective x-ray beams 5, the sentinel diodes 9will begin to produce a signal that can be used to speed up or slow downthe drive motor 11 and keep the array 8 moving synchronously with thex-ray beams 5. FIGS. 26 to 28 show the progression of the x-ray beams 5as they move from above a person in a wheelchair to below.

In this exemplary embodiment, the collimator 3 has a plurality of slitopenings 300, is mounted to the x-ray source 1 with an adjustablemounting bracket 200 and is rotated with a drive motor 111. Thesefeatures are shown in the enlarged view of the x-ray source 1 in FIGS.29 to 33. The mounting bracket 200 has two adjustable slides 202 and 204to align the collimator 3 with the focal spot of the x-ray source 1. Themounting bracket 200 also has an L-shaped bracket 206 that is rotated bydrive motor 111 to hold and position the collimator 3 in alignment withthe focal spot of the x-ray source 1. The collimator 3 has a set ofslots 2900 shaped to emit the x-ray beams 5 and adjustment assemblies208 that allow it to slide back and forth along the L-shaped bracket 206so that it can be aligned with the focal spot of the x-ray source 1.Once alignment has been achieved, the collimator 3 can be fixed in placewith set screws. The collimator 3 defines emission slots 290 foremitting the x-ray beams 5.

There are a number of embodiments of the system 1 that are possibleusing a fixed x-ray source 1 with a moving collimator 3 to produce oneor more scanning x-ray beams 5 and with one or more arrays 8. Theseembodiments include synchronization of the scanning x-ray beams 5 andthe arrays 8 by mechanical linkage (using mechanical arms 50 and 52) andsynchronization by microprocessor control using, for example, a feedbacksignal from the arrays 8 or sentinel diodes 9 to keep the detectors inthe arrays 8 in alignment with the x-ray beams 5 during the scan. Toacquire images of people sitting in wheelchairs 40, it is necessary toscan in two perpendicular planes (a vertical plane behind the person anda horizontal plane beneath them) in order to completely cover the entirevolume of space they occupy. In these embodiments, the x-ray source 1has an x-ray emission cone 55 that is at least 80 degrees high by 30degrees wide in order to cover a volume in the scanning booth largeenough to image a person sitting in a wheelchair 40. The x-ray source 1is placed approximately 2.2 meters from the arrays 8 and the totallength of the scanned image is at least 1.1 meters horizontally (underthe platform 21) and 2.2 meters vertically (behind the front wall 1900of the imaging cabinet 31). An exemplary embodiment of this is shown inFIGS. 26 through 33. As shown, the x-ray source 1 is fixed and thecollimator 3 is rotated by the motor 111 to sweep three of the x-raybeams 5 to scan an “L-shaped” area that is tracked by a set of threearrays 8 in the form of photodiodes to obtain an image of a personsitting in a wheelchair 40 on a platform 21. FIGS. 34 through 36 showthis same embodiment scanning a person standing on the platform 21.FIGS. 37 through 39 show the progression of the scan of this exemplaryembodiment without a person or a wheelchair present from above thesystem 1 and the array 8 below the platform 21 is shown moving from therear to the front of the system 1.

The embodiments described above that incorporate a fixed x-ray source 1and moving collimator 3 have a limitation that must be overcome withadditional shielding components in the aperture 4 of the generatorcabinet 30. This problem is illustrated in FIGS. 29 through 33. As shownin these figures, the x-ray emission cone 55 is intercepted by themoving collimator 3 as it moves up and down to create the scanning x-raybeams 5. The shape of the moving collimator 3 and its slit openings 300are determined by the distance of the collimator 3 from the focal spotof the x-ray generator 1. The collimator 3 must have a curved surfacewhose radius is equal to the distance from the collimator 3 to the focalspot of the x-ray generator 1 and must move along an arc whose radius isalso equal to the distance to the focal spot. It is advantageous to keepthe distance from the collimator 3 to the focal spot small to reduce theweight and size of the collimator 3 and to reduce the length of travelthat the collimator 3 must go through to scan the entire lengthrequired. If the x-ray source 1 is a mono-block generator, the size andshape of the generator prevents the collimator 3 from completelyblocking the entire x-ray emission cone 55 during the scan. As shown inFIGS. 29 through 33, the emission cone 55 of the x-ray source 1 extendsabove and below the position of the collimator 3 as it scans through theimage. See, for example, arrow A in FIG. 30. The arc length of thecollimator 3 must be kept short to prevent it from colliding with thex-ray source 1 at the top and bottom of the scan. The portion of thex-ray emission cone 55 that extends laterally on both sides of thecollimator 3 can be blocked by the aperture 4 in the front of the x-raygenerator cabinet 30. To prevent x-rays in the emission cone 55 that arenot blocked by the collimator 3 from escaping from the generator cabinet30, a set of lead blades is incorporated in the aperture 4 to interceptthe unblocked x-rays. These lead blades move up and down while thecollimator 3 is scanning. Alternatively, the collimator 3 has to bemoved farther away from the x-ray source 1 so that the arc length of thecollimator 3 can be extended enough to block the entire emission cone 55and not come in contact with the x-ray source 1 at the top and bottom ofthe scan. Doing this, however, increases the size and weight of thecollimator 3 and increases the arc length the collimator 3 has to travelto complete the scan.

If the x-ray source 1 was configured as a separate x-ray generator andx-ray tube, it is possible to make a collimator 3 with a sufficientlylarge arc length to block the radiation in the emission cone 55 bothabove and below the collimator 3 through its entire scan while keepingthe size and position of the collimator 3 small and compact. This is dueto the smaller size and shape of an x-ray tube compared with amono-block generator. The cylindrical shape of the x-ray tube is idealfor keeping the size and position of the collimator 3 small and compact.This reduces the size and cost of the drive motor 111 for the collimator3. An exemplary embodiment of the system 1 with an x-ray tube is shownin FIGS. 57 to 68.

Another limitation of the fixed-x-ray-source/moving-collimatorembodiments herein is that the precision required to keep the motion ofthe collimator 3 in synchronization with the motion of the arrays 8 isvery exacting. Because the collimator 3 is only about 10 percent of thedistance that the arrays 8 are from the focal spot of the x-ray source1, the precision of its travel must be 100-times greater than that ofthe arrays 8. In the embodiment where a mechanical arm 50 is used tokeep the collimator 3 and arrays 8 aligned during the scan, this is nota problem. In the microprocessor controlled embodiment of the scannergeometry, in comparison, the problem of the precision scanning ispresent although it removes the problem of blocking one side of thescanning platform 21 that the mechanical arm 50 presents. One way tomitigate the precision scanning problem and avoid needing a mechanicallinkage between the collimator 3 and arrays 8 is to fix the collimator 3to the x-ray source 1 and, instead of moving the collimator with respectto the x-ray source 1, move the x-ray source 1, itself, up and down tosweep the x-ray beams 5 through the scanning motion. In this fashion,because they move together, the collimator 3 always stays in alignmentwith the x-ray source 1 focal spot. Such an exemplary embodiment isillustrated in FIGS. 40 through 56.

FIGS. 40 to 47 show an exemplary embodiment of the system configurationwhere the x-ray source 1 is mounted in a frame 120 via two pivoting armassemblies 122. The pivoting arm assemblies 122 are attached, in thisexemplary configuration, to the sides of the x-ray source 1 and to thebottom of the frame 120. The pivoting arm assemblies 122 are mounted onthe x-ray source 1 in line with the focal spot of the x-ray source 1. Inthis way, the center of rotation of the x-ray source 1 is lined up withthe center of the focal spot of the x-ray source 1 so that, when thex-ray source 1 moves, it does so about the center of the focal spot. Thepivoting arm assemblies 122 include Y-shaped pivot arms 123 on eitherside of the x-ray source 1. The Y-shaped pivot arms 123 have inside ends124 fixedly attached to the x-ray source 1 and outside ends 125pivotally connected to the frame 120. Opposite the ends 124, 125 is amovement end 126 pivotally connected to the distal end of a telescopingarm 127 of a drive motor 128. Actuation of the drive motor 128telescopes the telescoping arm 127 in and out to translate the movementend 126 and rock the Y-shaped pivot arms 123 about their pivoting axisto, thereby, move the x-ray source 1 to sweep the x-ray beams 5 emittedthrough the collimator 3 through the scanning area and create the x-rayemission cone 55.

FIG. 42 illustrates the drive motor 128 having pivoted the pivot arms123 downwards to rock the x-ray source 1 upwards so that the x-ray beams5 are generated to impinge the vertical-moving arrays 8 at theirupper-most position and the horizontal-moving array 8 at its distal-mostposition. In contrast, FIG. 43 illustrates the drive motor 128 havingpivoted the pivot arms 123 upwards to rock the x-ray source 1 downwardsso that the x-ray beams 5 are generated to impinge the vertical-movingarrays 8 at a lower position and the horizontal-moving array 8 at anintermediate position. Similarly, FIGS. 44 to 47 illustrate similarmotion of this embodiment of the x-ray source 1. FIG. 44 illustrates thedrive motor 128 having pivoted the pivot arms 123 downwards to rock thex-ray source 1 upwards so that the x-ray beams 5 are generated toimpinge the vertical-moving arrays 8 at an upper-most position and thehorizontal-moving array 8 at its distal-most position. FIG. 45illustrates the drive motor 128 having pivoted the pivot arms 123slightly upwards to rock the x-ray source 1 downwards so that the x-raybeams 5 are generated to impinge the vertical-moving arrays 8 at a lowerposition and the horizontal-moving array 8 at an intermediate position.Finally, FIG. 46 illustrates the drive motor 128 having pivoted thepivot arms 123 slightly upwards to rock the x-ray source 1 downwards sothat the x-ray beams 5 are generated to impinge the vertical-movingarrays 8 at a lower-most position and the horizontal-moving array 8 at aproximal-most position.

Motion of the x-ray source 1 is controlled by the microcontroller 16 tokeep the motion of the arrays 8 in synchronization with the x-ray beams5. In this embodiment, alignment of the collimator 3 with the x-raysource 1 is assured because the collimator 3 is fixed to the x-raysource 1. The collimator 3 can be made long and wide enough so that itcompletely blocks all of the x-rays in the emission cone 55 fromescaping the x-ray generator cabinet 30. Various views of the collimatorare shown in FIGS. 44 to 47. Even though the collimator 3 is shown withopen sides in the various figures of the drawings, for example, in FIGS.40 and 41, to illustrate how the x-rays pass through the slots 2900 ofthe collimator 3, the x-ray source 1 has shielded sides in use toprevent undesired transmission of x-rays.

The mounting frame 120 of the x-ray source 1 is attached to a platforminside the x-ray generator cabinet 30. The platform has adjustableattachment points to secure the x-ray source 1 in a center of rotationof the focal spot at a height above the platform 21 to provide completecoverage of the scanning area. With the configuration described, FIGS.51 to 53 show how a person in a wheelchair can be scanned completelywith the x-ray source 1, and FIGS. 54 to 56 show how a person standingagainst the wall 1900 can be scanned completely with the x-ray source 1.

It is advantageous to use a mechanical linkage mechanism to align thearrays 8 with the x-ray beams 5 during the scan with a configurationhaving the mechanical mechanism not interfering with movement into andout from the scanning platform 21. It is also advantageous to mount thecollimator 3 onto the x-ray source 1 to eliminate any need to maintainalignment between the collimator 3, the x-ray source 1 focal spot, andthe arrays 8 during a scan. An exemplary embodiment having such featuresis presented in FIGS. 57 through 68. In this embodiment, the x-raysource 101 (which in this embodiment is an x-ray tube) is mounted on avertical cylindrical support post 130. The support post 130 has an uppersupport platform 140 for mounting thereon the x-ray source 101. Amounting and alignment bracket 150 connects the x-ray source 101 to thesupport platform 140 so that the focal spot of the x-ray source 101 isaligned with the central axis of the cylindrical support post 130, alsoreferred to as the x-ray source movement axis. For effecting suchalignment, the mounting and alignment bracket 150 can move the x-raysource 101 in both the X and Y directions on the support platform 140.

The support post 130 is mounted rotatably on a bearing 132 that allowsit to rotate freely about the vertical central axis of the support post130. An “L-shaped” mechanical arm 160 is attached to the bottom of thesupport post 130 and has a horizontal portion extending perpendicular toand away from the vertical axis of the support post 130 below the floorof the platform 21. A vertical portion of the arm 160 extends parallelto the vertical axis of the support post 130 behind the wall 1900. In anexemplary configuration, the horizontal portion of the mechanical arm160 extends away from the support post 130 by approximately 2.2 meters.At the distal end of the horizontal portion, the vertical portionextends vertically upwards for approximately 2.2 meters. The mechanicalsupport arm 160 is fixed to the support post 130 so that it rotates withthe support post 150. Such a configuration insures that the arrays 8 arealigned with the x-ray beam(s) 5. A first array 8 is mounted at thehorizontal portion beneath the platform 21 on which the person islocated. The second array 8 is mounted at the vertical portion of thearm 160. In this configuration, therefore, only a single x-ray beam 5needs to be emitted through the collimator 3 to intersect with both thehorizontal and vertical arrays 8. As the support post 150 is rotated,the x-ray beam 5 sweeps over the platform 21 to produce an image. Inthis configuration, the mechanical arm 53 that supports and aligns thearray 8 moves underneath the platform 21 and behind the wall 1900,thereby eliminating any egress restrictions encountered in previousembodiments described herein. FIGS. 58 and 59 illustrate various viewsof the system above the platform 160. The collimator 3 has one slitopening 300 and is mounted to the x-ray source 1 with an adjustablemounting bracket 200.

As shown in FIGS. 60 to 63, the mechanical arm 160 is rotated with asingle drive motor 111 through an angle sufficient to sweep the array 8across the entire width of the scanning platform 21 both in the floorand in the rear wall of the imaging cabinet 31. In an exemplaryembodiment, the drive motor 111 is connected to a ball screw or otherdrive mechanism that is further connected to the mechanical arm 160. Theposition and speed of the drive motor 111 is measured by an encoder. Inthis embodiment, only one drive motor 11 is required to drive the entireimaging assembly including the collimator 3 and the x-ray source 1. Themechanical arm 160 is supported by bearings and brackets to keep it fromflexing and, if desired, a port 170 in the platform can provide supportto the horizontal portion as shown in FIG. 57. The weight of the x-raysource 1 is supported by the support column 150, and the mechanical arm160 is also supported by bearings, greatly reducing the torque and powerrequired by the drive motor 111.

With the configuration described, FIGS. 64 to 66 show how a person in awheelchair can be scanned completely with the x-ray source 1, and FIGS.67 to 68 show how a person standing against the wall 1900 can be scannedcompletely with the x-ray source 1.

In accordance with another exemplary embodiment of the presentinvention, the x-ray exposure dose to the person being scanned ismonitored and controlled so that each person being scanned receives thelowest possible exposure. It is understood in the medical diagnosticx-ray field that x-ray beam quality plays an important role insimultaneously reducing the exposure dose and improving image quality.X-ray beam quality refers to the x-ray spectrum and intensity used toacquire the image. The x-ray spectrum is determined by the kilo-voltageapplied to the x-ray tube, by the anode material of the x-ray tube, andby the filtration used. The intensity of the x-ray beam is determined bythe electrical current applied to the tube and by the amount offiltration used. The beam quality that produces the lowest possible doseand highest image quality is a function of the anatomy and mass of theperson being exposed. Each person being scanned will have a uniqueanatomical profile and mass depending on their height and weight.Therefore, in this embodiment, the parameters of the person's anatomicalprofile are measured before each scan is made in order to determine therequired beam quality parameters for administering the lowest possibledose.

In accordance with an exemplary embodiment, a dosimeter is positioned inthe x-ray beam 5 to measure and record the x-ray exposure producedduring each scan. A set of filters are positioned in front of thecollimator 3 to filter the x-ray beam 5. Immediately before a person isscanned, the mechanical arm 50, 160 is positioned in the center of theplatform 21 and a single row of image data is acquired using a nominalset of exposure parameters (e.g., 100 kV and 0.3 mA). A histogram of theimage data produced is analyzed to determine the amount of attenuationin at least three segmented areas of the line of image data to determinethe distance from the top of the head to the abdominal region, theextent of the abdominal region, and the distance to the feet. These datavalues are used to determine the extent and type of filters to use andthe optimum x-ray exposure parameters to use (e.g., kV, mA, and scanningspeed) during the scan to produce the lowest dose and best image qualityfor the person being scanned.

An ideal histogram of image data is one where the average intensity ofthe pixels within the anatomical region (where x-rays are attenuated bythe body) is approximately half of the maximum value and where thedistribution of values around the average as large as possible but lessthan half of the average intensity. Within each line of image data, atleast three segmented regions of image values exist: (1) a portion of aline where un-attenuated x-rays impinge on the detectors; (2) a portionof a line where x-rays pass through the extremities (arms, head, andlegs) of the person being scanned; and (3) a portion of a line wherex-rays pass through the chest and abdominal region. The ideal x-rayspectrum used to image human anatomy is one that has very little soft(low energy) x-rays and has a maximum energy (kV) that is just largeenough so that the majority of the x-rays pass through the anatomy. Softx-rays are absorbed almost entirely by the anatomy and do not reach thedetector, so they only contribute to exposure dose but not to the imagequality. Higher energy x-rays penetrate better and provide a betterdose-to-image quality relationship but also produce a lower detectorresponse as energy is increased. The lower detector response at higherx-ray energy is driven by the response of the scintillating phosphor,which has a reduced efficiency at x-ray energies above 60 keV. Filterssuch as aluminum and copper are used to optimize beam quality formedical diagnostic x-ray imaging because they preferentially absorb thesoft, lower x-ray energies of the x-ray spectrum, thereby reducing theamount of exposure dose and improving the dose efficiency. Accordingly,it is necessary to adjust the maximum kV and spectrum of the x-rays usedto image human anatomy in order to maximize the dose efficiency in termsof the amount of x-ray exposure dose used to make a given image quality.

The foregoing description and accompanying drawings illustrate theprinciples, exemplary embodiments, and modes of operation of theinvention. However, the invention should not be construed as beinglimited to the particular embodiments discussed above. Additionalvariations of the embodiments discussed above will be appreciated bythose skilled in the art and the above-described embodiments should beregarded as illustrative rather than restrictive. Accordingly, it shouldbe appreciated that variations to those embodiments can be made by thoseskilled in the art without departing from the scope of the invention asdefined by the following claims.

What is claimed is:
 1. A scanning transmission x-ray imaging system thatminimizes x-ray exposure dose on a subject, the system comprising: anx-ray platform at which the subject is to be x-ray scanned from one endof the subject to the other end; an x-ray source producing x-rays at afocal spot that does not move with respect to a stationary subject beingimaged, the x-ray source pivoting about a source movement axis passingthrough the focal spot to scan the subject; at least one x-ray detectorarray having a detector dimension with a height and a width anddetecting x-rays from the x-ray source along the detector dimension; acollimator disposed between the x-ray source and the at least onedetector array, fixed to the x-ray source, and defining at least oneslit to collimate the x-rays into a linear x-ray beam; the at least onex-ray detector array: being spaced from the x-ray source such that thelinear x-ray beam at the at least one x-ray detector array substantiallyimpacts within the height and the width of the detector dimension; andbeing operable to move and thereby keep the linear x-ray beam alignedwith the at least one x-ray detector array; a controller programmed: tomove the at least one x-ray detector array and keep the linear x-raybeam aligned with the at least one x-ray detector array; and before thesubject is scanned, to move the at least one detector array to anintermediate position of the x-ray platform and acquire at least one rowof image data using a nominal set of exposure parameters and, based uponthe image data acquired, determine beam quality parameters foradministering a lowest possible dose for the subject.